1. Field of the Invention
The present invention relates to a system and method for tracking of individuals in general and in particular to a network system and method for tracking and monitoring persons by using a communication line as well as radio frequency transmitters and receivers, working in conjunction with a central monitoring system which is capable of collecting and summarizing the activity of the system.
2. Discussion of the Related Art
Persons tracking and monitoring systems use wireless and GPS (Geographical Positioning System) technology for tracking persons such as offenders, mentally incapacitated or inapt persons. Such tracking of persons may be required medically or legally by the court system.
One persons monitoring system involves the use of a limb worn short range radio frequency (RF) transmitting device (tag), a body worn GPS localization and wireless transmission device, also known as Localization and Transmission Device, (LTD) and a central monitoring station (CMS) for receiving wireless information from body worn devices. The tag communicates with the LTD for the purpose of assurance that the LTD is in close proximity with the monitored person. The tag typically has an anti-tamper mechanism. When a monitored person is tampering with the transmission or the tag device or attempts to remove the tag from the limb, a wireless communication message is transmitted to the central monitoring station (CMS). Some similar applications also include a panic button. The panic button sends a wireless communication message routed to the central monitoring station. The body worn LTD is functional in geographical localization of said device and for the transmission of the location to a central monitoring station (CMS) via wireless communication. The geographical localization in such a system is realized via GPS technology. Through the operation of a GPS receiver located within the LTD, the geographical location of the LTD and a time stamp are temporarily stored in a memory device within the LTD and then transmitted via wireless communication to the CMS. The wireless transmission is thus routed through a local wireless network. Some systems have the capability to connect to a stationary device for transmission of location and time stamp information via landline. This feature is performed only when the monitored person is at home or at a base station where such a device is located. The CMS is typically a computer connected to the wireless network. The CMS receives the transmissions sent from the different LTD's, processes and displays the transmissions to the monitoring personnel. The processing involves summarizing the location and time stamps of each LTD monitored by the system as well as the status of the LTD and tag, such as battery level, anti-tamper mechanism condition, etc. The computer of the CMS also plots the location of the LTD's given by the GPS coordinates received from overhead satellites as a function of time stamp also received from said satellites on an electronic map generated by the computer. In some peoples tracking systems, the personnel monitoring the system can set rules and regulations for each monitored person. Such rules are referred to in the art as location and time constrictions rules. Location and time constriction rules are sent via wireless network to the appropriate LTD where they are stored in the LTD's memory. The LTDs constantly compare the location and time stamp obtained from the GPS with the rules stored in their memory device. These rules are intended for example, for the prevention of a monitored person from being present in a certain location at a specific time frame. For example, a person may be barred from entering a two-mile radius or zone from the house of a victim. In a characteristic operation of such a system, if a person violates the rules set up by the system, a wireless message is sent to the CMS. Personnel monitoring the system in the CMS can then alert law enforcing agents in order to intercept the person, as well as send a warning message to the LTD located on the person.
The present offered systems of the kind described above have several drawbacks. For an estimate of the LTD location and time stamp using GPS technology, at least four orbiting satellites are required. In locale and during time periods where satellite cover is inadequate, the systems ability to track the monitored persons is diminished or non-existent. In addition, the use of a GPS receiver is power demanding and requires the use of high-energy battery.
The above-mentioned persons tracking system uses wireless communication for the transmission of information between the LTD's and the CMS. However, wireless communication may be hampered by crowded wireless systems. Tracking and monitoring systems of the GPS/wireless type are intended for use mainly in urban areas that are already heavily crowded with cellular communications. In addition, the loss of wireless connection in conditions of reduced reception can also hamper the systems operation. This is important especially around sensitive locale such as in and around victim's houses, banks, work places and the like, where the wireless network often has diminutive reception. There is therefore a need in the art for a persons tracking and monitoring system that is independent of GPS technology or wireless communication such that the lack of satellite coverage and wireless communication coverage will not impede tracking and monitoring. There is a need for a system that can track and monitor a person around specific locations at specific times and at the same time uses relatively cheap and low weight carried equipment by the monitored person.
An RF only based monitoring system involves the use of local radio frequency (RF) signals for the localization of individuals who are monitored. In such a system the monitored person is wearing a one way RF transmitting tag. This tag is transmitting periodically and could also be fitted with some anti-tamper and panic mechanisms. The RF signals emanating from the tag are received by a local monitoring (receiving) device typically situated in an area where the person spends most of his time such as in the person's house. The local monitoring device is tuned to identify only to the specific tag worn by the person. When the person wearing the tag is located within the reception range of the local monitoring device, the tags identification code and a time stamp is sent to a central monitoring system via telephone for processing and display. A drawback of this system includes the small coverage area of the system as a whole and the rigid association of local monitoring device to a specific tag. The monitoring system mentioned above is limited by the limited reception range of the single local monitoring device tuned to one tag. People wearing a tag can only be monitored when in range of the specific monitoring device, typically around their house. Thus when a person wearing a tag is away for shopping, visiting friends etc. he is not monitored and his whereabouts are unknown.
There is therefore a need for a monitoring system that is able to monitor any person wearing an RF transmitting tag over various locations in a cost effective manner. There is a need for a monitoring system using a light weight tag which is capable of placing monitored persons to specific locations while using small and relatively cheap system components for the intended task.